It is known that charging stations for electrically driven vehicles are provided with two or more charging points. In this case, two or more vehicles can be charged at the same time at said individual charging points. The transformer apparatus serves here firstly to distribute power to the individual charging points.
Modern electric vehicles generally allow two charging modes. A vehicle has an on-board charging device for charging at a conventional AC voltage or three-phase connection, said charging device both performing the required conversion to direct current and controlling the respective charging operation. However, this AC charging mode is extremely restricted in terms of charging speed on account of the connection power available, which is generally not more than 16 A or 32 A, and on account of the installation of the charging device with sufficient power. In modern electric vehicles, this results in charging times of several hours every 100 km. Rapid DC charging, preferably using DC voltage, has been developed on account on the high charging times for AC charging. In contrast to AC charging, the electrical operating means and components required for charging to this end are not carried concomitantly in the vehicle but are provided by a charging column outside of the vehicle. The charging column performs the charging process and thus forms voltage and current on demand of the vehicle, as is necessary for charging the respective vehicle battery. Correspondingly provided DC charging lines are electrically connected to the poles of the high-voltage battery of the vehicle by various contactors in the vehicle during the charging process. The powers of conventional DC charging stations are currently typically up to 50 kW and are generally drawn directly from the low-voltage grid or local grid. However, charging powers of more than 300 kW would be desirable in order to surpass charging speeds of more than 20 km/min. Furthermore, charging voltages of up to 1000 V are sought in order to charge batteries of future vehicles with 600 V or even above 800 V battery voltage and to achieve higher charging powers with low charging currents. Exemplary details regarding DC charging are described, inter alia, in IEC 61851, which is incorporated by reference herein. To charge vehicles with more than 300 kW power, drawing the energy from the low-voltage grid or local grid is not conducive to grid stability and the connection to the medium-voltage distribution grid or in future even the high-voltage grid offers significant advantages.
Patent application DE 10 2012 212 291, which is incorporated by reference herein, describes a system for electrical DC-voltage charging, which system has at least one DC/DC regulator module comprising a DC/DC step-down module without DC isolation and a DC/DC resonant converter module with DC isolation.
Patent applications DE 10 2015 110 023, which is incorporated by reference herein, and DE 10 2016 123 924, which is incorporated by reference herein, describe apparatuses for DC-voltage charging of electric vehicles, which apparatuses operate in technical circles under the name “split powerline.” In this case, the desired DC isolation of the individual charging connections or charging points of a charging park from the energy grid and from one another is achieved by a transformer having separate secondary windings. The advantage of this technology lies in the possible use of non-DC-isolating operating means, which are cost-effective and expedient in terms of installation space, such as, for example, rectifiers, AC/DC converters and DC/DC converters subsequent to the respective secondary windings. The mentioned transformer can in this case be fed from a low, medium or high voltage using appropriate coil ratios. In this technology, the transformer provides, on the one hand, the energy for the charging points, as well as the DC isolation. The alternating current of the secondary windings of the transformer is in this case generally converted to a direct current by a rectifier or an AC/DC converter, which direct current can also optionally be adapted in terms of the voltage and can be further modeled in terms of its physical properties, for example the current ripple, by a downstream DC/DC converter. The DC-voltage output can be fed to a vehicle via a charging cable. The secondary windings can in each case be single-phase or polyphase windings.
A disadvantage of the known solutions and, in particular, of split powerline technology is that the number of charging points at a charging station for an individual transformer apparatus leads to a significant increase in complexity, physical size and costs. According to the prior art, transformers generally have to be developed in an application-specific manner and adapted for each charging park and also load scenarios of the individual charging points. Furthermore, in particular, an asymmetrical charging situation or an asymmetrical construction situation of different charging functions, different charging powers or different charging points has to be taken into account in the transformer apparatus. In this case, it should be pointed out, in particular, that different charging points can be, or even in some charging situations have to be, supplied with different electrical powers. This can be done, inter alia, in a flexible manner too when, for example, different vehicles at two charging points require different electrical charging powers. However, it is also conceivable for the transformer apparatus to have to supply different charging points with always a different electrical power in a structurally fixed manner. In both cases, the known transformer apparatuses are only insufficiently designed for this flexibility. Said flexibility therefore has to be taken into account in the construction from the outset and provided with appropriate large, complex and expensive construction technology in the transformer apparatus.